1. Field of the Invention
The present invention relates generally to master cylinders for vehicles and, more particularly, to a master cylinder which generates hydraulic pressure in a hydraulic brake system of a vehicle.
2. Description of the Related Art
Generally, master cylinders for vehicles are apparatuses for generating hydraulic pressure when brake pedals are applied.
In hydraulic brake systems for vehicles, oil supplied from an oil reservoir is compressed by a master cylinder to generate liquid pressure. The liquid pressure is transmitted to wheels through a brake hydraulic pressure line.
The liquid pressure transmitted to the wheels brings a brake shoe or disc into contact with the inner surface of a brake drum, thus generating friction braking force.
FIGS. 1 and 2 are views showing a path along which oil is drawn into a master cylinder 10 for a vehicle, according to a conventional technique.
Referring to FIG. 1, the conventional master cylinder 10 includes a housing 11 in which a liquid pressure chamber 12 is formed, a piston 13 which reciprocates in the liquid pressure chamber 12, an inlet port 15 which supplies oil into the liquid pressure chamber 12, and a seal 16 which allows or interrupts the supply of oil into the liquid pressure chamber 12.
A plurality of bypass holes 14 is formed in the piston 13 to provide a path along which oil is supplied from the inlet port 15 into the liquid pressure chamber 12.
When the piston 13 is in an initial stationary state or when the piston 13 linearly moves and the bypass holes 14 formed in the piston 13 are positioned within a range of the seal 16 (in other words, when the bypass holes 14 are positioned adjacent to the inlet port 15), oil is allowed to be supplied into the liquid pressure chamber 12 through the bypass holes 14.
Referring to FIG. 2, when the piston 13 linearly moves and the bypass holes 14 are beyond the edge of the seal 16 (in other words, the seal 16 is positioned between the bypass holes 14 and the inlet port 15), the edge of the seal 16 is brought into contact with the circumferential outer surface of the piston 13.
The contact between the piston 13 and the seal 16 interrupts the path along which oil is supplied into the liquid pressure chamber 12, so that oil supplied from the inlet port 15 cannot be drawn into the liquid pressure chamber 12 through the bypass holes 14.
However, in the master cylinder according to the conventional technique having the above-mentioned construction, because the plurality of bypass holes 14 is formed in the piston 13, the costs required to process the master cylinder are increased. Furthermore, due to presence of the bypass holes 14, there is a problem in that the overall length of the master cylinder is increased.